1. Field of the Invention
The present invention relates generally to explosive materials and, more particularly, to a composition and method for applying a moisture barrier coating to an explosive material.
2. Technical Considerations
Explosive compositions generally consist of a fuel component and an oxidizer component. Many known compositions utilize organic or inorganic nitrates as the oxidizer component in combination with an organic acid as the fuel component. These combustible compositions have utility as gunpowder, explosives, propellants, and pyrotechnic applications. Depending on the characteristics of the fuel component, the oxidizer component, and/or the explosive composition as a whole, differing explosive compositions will perform differently. Some explosive compositions perform best as deflagrating agents or propellants. Other explosive compositions are utilized as detonating compounds. Still other explosive compositions are utilized in pyrotechnic applications.
Typically, gunpowder, propellants, and other particulate explosive materials are manufactured by methods which yield a product having a moisture content substantially higher than that ultimately desired. By way of example, gunpowder of the type generally known as xe2x80x9cblack powderxe2x80x9d is one explosive composition which has been used for centuries as a propellant, deflagrating agent, explosive, and pyrotechnic compound. Conventional black powder is commonly composed of an intimate mixture of potassium nitrate, sulfur, and charcoal, wherein the potassium nitrate is the oxidizing agent while the sulfur and charcoal constitute the fuel component Black powder, as with most gunpowders, also exhibits some degree of hydroscopicity, which can limit product life and create unpredictability in performance. By xe2x80x9chydroscopicityxe2x80x9d is meant the absorption of water, such as from the atmosphere. Excessive moisture in any explosive material can create a dangerous condition for the user. It is desirable to have predictable performance of an explosive composition when it comes to safe handling, burning, and detonation of an explosive material.
By way of example, explosive material, such as certain rocket propellants, can typically have moisture contents as high as 70% or more by weight, which is substantially higher than that which is ultimately desired. Also, due to the hydroscopicity of the explosive material, the product life or shelf life of the explosive material can be limited by accumulating or attracting moisture, thereby creating unpredictability in performance.
Another way an explosive material can accumulate moisture is by exposure to outdoor environments, such as rain or high humidity. For example, black powder is used by many hunters who use muzzleloader rifles during hunting season. Some states even have a special black powder season for hunters who hunt with muzzleloader rifles. In this outdoor environment, the black powder may become damp when loading it into the muzzleloader rifle. Excessive moisture in the black powder can cause the muzzleloader to misfire, thus either creating a potentially dangerous condition or simply inconveniencing the hunter.
It is, therefore, an object of the present invention to overcome at least some of the above deficiencies by providing a coating composition and coating method that provide a moisture barrier for explosive materials. It is also an object of the invention to provide a moisture barrier coating and/or coating method which will not substantially adversely affect the properties or characteristics of the explosive material. Another object of the present invention is to reduce the moisture content of the explosive material by removing residual moisture as a coating composition of the invention is applied to the explosive material.
The present invention provides a composition and a method for treating an explosive material by coating the explosive material with a composition of the invention, thereby providing a moisture barrier to the explosive material. The method includes providing a waterproofing composition and subsequently coating an explosive material with the composition to produce a moisture barrier. In one embodiment, the composition can comprise a reaction product of from 25 to 40 percent by weight of at least one polyisocyanate, such as 33.1 percent by weight; from 45 to 85 percent by weight of a polymer derived from 1,3-butadiene and containing functional groups that are reactive with an isocyanate group, such as 66.2 percent by weight; from 0.005 to 0.05 percent by weight of an aromatic isocyanate, such as 0.02 percent by weight; from 0.005 to 0.05 percent by weight of a catalyst, such as 0.02 percent by weight; optionally from 0.05 to 1.5 percent by weight of a drying agent, such as 0.66 percent by weight; and optionally from 1 to 25 percent by weight of a solvent, all percentages by weight being based on the total weight of the composition.
A method for preparing a composition for waterproofing explosive materials is also provided and comprises:
a. mixing a plurality of chemical components comprising:
i) 25 to 40 percent by weight, based on the total weight of the composition, of at least one polyisocyanate;
ii) 45 to 85 percent by weight, based on the total weight of the composition, of a polymer derived from 1,3-butadiene and containing functional groups that are reactive with an isocyanate group; and
iii) 0.005 to 0.05 percent by weight, based on the total weight of the composition, of an aromatic isocyanate;
b. adding a catalyst in a range of from 0.005 to 0.05 percent by weight, based on the total weight of the composition, to the components in step a; and
c. allowing the components to react.